Before the Isle of the Lost
After Merlin transforms Arthur into a bird, Arthur finds himself pursued by a hawk and subsequently flees into the woods. He unwittingly perches atop the abode of Madam Mim, ducking into her chimney as the hawk swoops once more at him in a predatory lunge. Arthur surprises Mim with his inadvertent arrival. Mim tries to convince Arthur that she is superior to Merlin, but Arthur remains unconvinced, citing Merlin's benevolence when using magic. This infuriates Mim, being that she sees all good things as bad ("Yes, and in my book, that's bad!"), so she decides to kill him . She transforms into a cat and captures Arthur, but Merlin appears in a whirlwind and prevents Mim from destroying Arthur by interrupting her. (Archimedes had just previously alerted Merlin regarding Arthur's whereabouts.) This results in a "Wizards' Duel" between her and Merlin for the young boy's life. Mim consistently cheats throughout the duel, breaking each of her self-set rules every time she shape-shifts. Mim initially has the upper hand (especially after transforming into a dragon), but Merlin outsmarts her by transforming into a germ and infecting her. She is last seen at home in her bed, recovering from the disease. Merlin advises her to get plenty of rest and sunshine, opening a hole in her roof as he speaks. Mim rants about how much she hates sunshine as Merlin and the other two depart.
Madam Mim was introduced as one of the villains imprisoned in the Isle of the Lost and was revealed to have granddaughters of her own (before Mad Maddy was introduced).
Madam Mim makes her official appearance near the end of the novel. She had found an underground tunnel that led to Auradon, and attacked Camelot Heights in dragon form. Many suspected it to be Maleficent until after much investigation.
Mal's team, Ben, Merlin and Grumpy stumble across Madam Mim in the dwarf mines, where a battle commences until Ben turns the tide by pointing Excalibur to her chest. Merlin then sends her back the Isle of the Lost.
- She is the second Disney Villain to turn into an animal. The first was Maleficent, the third was Jafar, the fourth and fifth were Pain and Panic, and the sixth was Yzma.
- She is the second female Disney Villain to have a song. The first was the Queen of Hearts, the third was Ursula, and the fourth was Mother Gothel.
- She was voiced by Martha Wentworth in her debut, The Sword In The Stone.
- In Return to the Isle of the Lost, its mentioned that she almost burned down Sherwood Forest. This may prove that she and Robin Hood fought against each other and was defeated after she escaped the Isle of the Lost.
- She is the second villainess to have a male protagonist in her debut. The first was Cruella De Vil and the third was Yzma.
- Madam Mim's crimes were
- Cheating in The Wizards Duel
- Attempted Murder (Merlin, Arthur)